Biomedical subjects

K Tamura

Publications and source records attributed to K Tamura.

At least 73 records · Page 4Linked to original sources

PubMed2001

EXAFS measurements for liquid Ge-Si alloys.

EXAFS measurements around the Ge-K edge have been carried out for liquid Ge-Si alloys for the first time to investigate the local structure around a Ge atom. To perform the EXAFS measurements for the liquid alloys with high melting temperatures, a new sapphire cell have been developed. The measurements were carried out for the liquid alloys from 10% to 60% of Si and the crystalline ones from 10% to 70% of Si as a reference. EXAFS oscillations, x(k), are observed even at 1480 degrees C for liquid Ge(0.4)Si(0.6). The position of the first peak in the radial distribution function obtained from Fourier transform of x(k) is shifted towards smaller distance for liquid and crystalline alloys with increasing Si concentration. The results of a curve-fit analysis in a harmonic approximation show that Ge-Ge and Ge-Si bonds in the liquid alloys become long with increasing Si concentration while those become slightly short in the crystaline ones.

Journal Article↗

PubMed2001

Ubiquitin-mediated degradation of hepatitis C virus core protein is regulated by processing at its carboxyl terminus.

Hepatitis C virus core protein, in addition to being a component of the viral capsid, has a number of regulatory functions. Here we showed two bodies of evidence indicating that a fraction of the core protein species is a substrate of the ubiquitin (Ub)-proteasome pathway of targeted proteolysis. First, the core protein processing the C-terminal hydrophobic region is metabolically unstable, and incubation with a proteasome inhibitor led to a significant accumulation of the protein. Second, an in vivo ubiquitylation assay indicates conjugation of multi-Ub chain to the unstable core protein. In contrast, a stable form of core protein, p21, is also able to be ubiquitylated, but it links to a single or only a few Ub moiety. Therefore, processing event(s) at the C-terminal hydrophobic domain of HCV core protein may affect the ubiquitylation pathway, particularly the efficiency of the multi-Ub chain assembly, resulting in stable, matured core proteins.

Binding Sites↗

PubMed2001

Oligonucleotide-directed peptide synthesis in a ribosome- and ribozyme-free system.

Peptide bond formation by the ribosome requires 23S rRNA and its interaction with the 3'-CCA end of tRNA. To investigate the possible evolutionary development of the peptidyl transfer reaction, we tried to obtain peptide bond formation without the ribosome or rRNA simply by using a piece of tRNA--an aminoacyl-minihelix--mixed with sequence-specific oligonucleotides that contained puromycin. Peptide bond formation was detected by gel electrophoresis, TLC analysis, and mass spectrometry. Peptide synthesis depended on sequence complementarity between the 3'-CCA sequence of the minihelix and the puromycin-bearing oligonucleotide. However, proximity of the reacting species was not by itself sufficient for peptide bond formation. In addition, imidazole as a catalyst was required. Its role may be similar to the recently proposed mechanism, wherein A2451 of 23S rRNA works as a general base. Thus, peptide bond formation can be achieved with a simple, minimized system that captures the essence of an interaction seen in the ribosome.

Base Pairing↗

PubMed2001

An epidermal signal regulates Lmx-1 expression and dorsal-ventral pattern during Xenopus limb regeneration.

The results of recent studies have supported the idea that the ability to organize the formation of axes such as the anteroposterior and proximodistal axes corresponds to limb regeneration ability in Xenopus. In this study, we investigated the mechanism by which the dorsoventral (D-V) axis of regenerating Xenopus limbs is established and the relationships between D-V patterning and regenerative ability. Transplantation experiments were performed to study which epidermis or mesenchyme is responsible for the D-V patterning in regenerating limbs. Naked mesenchyme of a donor limb was rotated and implanted on a host opposite-side limb stump to make a reversed recombination about the D-V axis. The resultant regenerates had a normal-looking D-V pattern, including Lmx-1 expression, muscle pattern, and joints, in stage 52 recombinants and a reversed D-V pattern in stage 55 recombinants. Further experiments in recombination at stage 52 and stage 55 showed that the epidermal signal is responsible for producing the D-V pattern in the regenerating blastema. These results, together with the finding that Lmx-1 expression is absent in the froglet forelimb blastema, suggest that D-V axis formation is a key step in understanding the loss of regenerative ability.

Amino Acid Sequence↗

PubMed2001

Metabolic engineering of plant alkaloid biosynthesis.

Plant alkaloids, one of the largest groups of natural products, provide many pharmacologically active compounds. Several genes in the biosynthetic pathways for scopolamine, nicotine, and berberine have been cloned, making the metabolic engineering of these alkaloids possible. Expression of two branching-point enzymes was engineered: putrescine N-methyltransferase (PMT) in transgenic plants of Atropa belladonna and Nicotiana sylvestris and (S)-scoulerine 9-O-methyltransferase (SMT) in cultured cells of Coptis japonica and Eschscholzia californica. Overexpression of PMT increased the nicotine content in N. sylvestris, whereas suppression of endogenous PMT activity severely decreased the nicotine content and induced abnormal morphologies. Ectopic expression of SMT caused the accumulation of benzylisoquinoline alkaloids in E. californica. The prospects and limitations of engineering plant alkaloid metabolism are discussed.

Alkaloids↗

PubMed2001

Expression of Bcl-2 and p53 protein in resectable invasive ductal carcinoma of the pancreas: effects on clinical outcome and efficacy of adjuvant chemotherapy.

BACKGROUND AND OBJECTIVES: p53 tumor suppressor gene has a dual role as a trigger of apoptosis and as an initiator of DNA repair. The Bcl-2 can work to protect cells from apoptosis, which is induced by p53 gene. These facts suggest the significant role of these genes in the genesis and progression of various tumors. The present study was designed to assess the significance of p53 and Bcl-2 protein (pBcl-2) expression on resectable invasive ductal carcinoma (IDC) of the pancreas. METHODS: The present study included 63 IDCs, which were resected between 1982 and 1998. pBcl-2 and p53 were stained immunohistochemically with monoclonal antibodies. RESULTS: pBcl-2 was expressed in 16 (25.4%), and p53 was positively expressed in 32 out of 63 IDCs (50.8%); however, expression of pBcl-2 did not necessarily correlate with that of p53. Although p53 expression did not show any significant influence on the patients' survival, pBcl-2(+) patients showed a higher survival than pBcl-2(-) patients for both p53(+) and p53(-) patients, which suggested that pBcl-2 expression had a more significant effect on the survival of patients than p53 expression. On the other hand, there were no differences in the survival curve between the adjuvant chemotherapy (ACT) group and the surgery alone (SA) group. pBcl-2 expression had no influence on the effect of ACT, the ACT group showed a significantly better survival than the SA group for p53(+) IDC patients. CONCLUSIONS: pBcl-2 expression is a beneficial prognostic factor for patients with IDC, whereas p53 expression may be beneficial in the prediction of the effects of adjuvant chemotherapy on patients with IDC. J. Surg. Oncol. 2001;76:188-196.

Adult↗

PubMed2001

Comparison of plastic prostheses and self-expandable metallic stents in the treatment of malignant esophageal stenosis.

OBJECTIVE: We compared the efficacy of plastic prostheses and self-expandable metallic stents in the treatment of malignant esophageal stenosis and/or fistula. SUBJECTS AND METHODS: Subjects were 31 patients with esophageal cancer, 4 with esophagotracheal fistula, and 1 with esophageal stenosis. A plastic prosthesis was inserted in 15 patients (group A) and a self-expandable metallic stent in 21 patients (group B). We evaluated food ingestion improvement, effectiveness, complications, mean survival, food ingestion duration, the percentage of food ingestion capability in total survival time, and inhospital mortality. RESULTS: No differences were seen in food intake improvement or in the effectiveness between groups, whereas fatal complications were higher in Group A. No significant differences were seen in mean survival, food ingestion duration, percentage of food ingestion capability, or inhospital mortality between groups. CONCLUSION: We concluded that a self-expandable metallic stent was safer than a plastic prosthesis because of fewer serious complications such as bleeding, and recommended the use of metallic stents in the treatment of malignant esophageal stenosis and/or fistula.

Aged↗

PubMed2001

Stimulation of MCM3 gene expression in osteoblast by low level laser irradiation.

Biostimulatory effect of cell proliferation and bone formation by laser irradiation has been reported, however, very little is known about the molecular basis of mechanisms. We previously constructed the cDNA library of mouse osteoblastic cells (MC3T3-E1) which enhanced gene expression by laser irradiation using a subtracted gene cloning procedure. In the present study, we focused on a gene clone, designated as MCL-140, which exhibited the high homology of DNA sequence with mouse minichromosome maintenance (MCM) 3 gene. MCM3 is involved in the initiation of DNA replication as licensing factor in eukaryotic cells. Nucleotide sequence of MCL-140 insert was determined and assessed in the nucleic acid databases. The transcription level of MCL-140 was examined by Northern blot analysis. The DNA sequences of clone MCL-140 insert exhibited 96.2% homology with MCM 3 gene coding P1 protein. Higher MCM3 mRNA levels were observed in laser-irradiated cells compared to the levels in non-irradiated cells: furthermore, radiolabelled thymidine incorporation was increased by laser irradiation. These findings suggest that low-level laser irradiation may enhance DNA replication and play a role in stimulating proliferation of osteoblast through the enhancement of the MCM3 gene expression.

Animals↗

PubMed2001

Analysis of the immunoglobulin heavy chain gene variable region of intravascular large B-cell lymphoma.

Intravascular large B-cell lymphoma (IVLBL) is a rare neoplasm characterized by proliferation of lymphoma cells within the blood vessels. The cell origin of IVLBL has not yet been determined. We examined cell lineage, with immunohistochemical staining and molecular analysis, using polymerase chain reaction (PCR) of the variable region of the immunoglobulin heavy chain (Ig-VH) gene. We also investigated the cell origin using direct sequence analysis of the complementary-determining region 2 (CDR2) and framework region 3 (FR3) in six cases, consisting of two male and four female patients. The sequences in five cases showed frequent mutations. The percent homology to their closest germline genes ranged from 74.7 to 91.8%. However, one case showed a percent homology of 99.4% in CDR2 and FR3 of Ig-VH. All cases showed rearrangements of VH3 family genes. Interestingly, three of the IVLBL cases with hypermutated IgH genes showed the expression of CD5. Therefore, expression of CD5 in lymphoma cells does not indicate that the origin of IVLBL is the same as mantle cell lymphoma having the character of CD5 expression, which develops in pre-germinal center cells. Our results indicate that most IVLBLs may originate in the post-germinal center cells, based on the presence of somatic mutation in VH genes, although some heterogeneous cases are intermingled within IVLBL.

Aged↗

PubMed2001

The importance of peripheral blood leukocytes and macrophage infiltration on bronchial wall wound healing in rats treated preoperatively with anticancer agents.

Preoperative chemotherapy is commonly used for small cell lung cancer or advanced non-small cell lung cancer. This study was conducted to investigate the effects of preoperative antineoplastic agents on the postoperative would healing of bronchial anastomoses in a rat model. Cisplatin (CDDP), doxorubicin (ADM), or cyclophosphamide (CPA) was administered either 3 days preoperatively (experiment 1) or 7 days preoperatively (experiment 2). Wound healing was assessed on postoperative days (POD) 3, 5, and 7 after anastomosis of the bronchus, by examining the bursting strength and hydroxyproline tissue content. In experiment 1, significant impairment of wound healing was seen on POD 3 in the CPA-treated rats, but no significant changes were seen in the other groups. Severe leukopenia and marked reduction of macrophage infiltration into the wound were also observed in the CPA-treated rats. The impairment of wound healing coincided with the time of leukopenia and reduced macrophage infiltration into the wounds. In experiment 2, induction chemotherapy did not impair wound healing. Our experimental results suggest that preoperative chemotherapy producing mild leukopenia, or when followed by a sufficient interval to allow for the recovery of myelosuppression, did not impair wound healing of the bronchial anastomoses. The findings of this study also showed that the depletion of macrophages at the anastomotic site is one of the most important causes of impaired wound healing.

Anastomosis, Surgical↗

PubMed2001

Oligoclonal expansion of alphabeta T lymphocytes in Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis with abnormal karyotypes.

We observed a fatal case of Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis (HLH) with an abnormal karyotype. Increased levels of alphabeta T cells of the patient were investigated using an inverse polymerase chain reaction (PCR) of the T-cell receptor variable region gene, followed by Jbeta-PCR and single-strand conformation polymorphism (SSCP) to confirm the clonality of specific alphabeta-T cell subsets. A high frequency (>15%) was recognized in Vbeta9 at onset, but not in any Vbeta and Valpha families 2 weeks after chemotherapy. High levels (>20%) of some Jbeta genes were detected in all Vbeta families investigated, and the predominant bias of the Jbeta2 gene relative to the Jbeta1 gene (86.1% versus 13.9% at onset, and 77.4% versus 23.5% after chemotherapy) was recognized in pan-alphabeta T cells. When each Vbeta-Jbeta fragment was compared among the samples at onset and after chemotherapy by SSCP analysis, several distinct bands were observed that indicate a clonal evolution. Thus, the findings suggest that some of the alphabeta T cell clones could be associated with abnormal karyotypes in EBV-HLH. The present findings provide molecular evidence of the presence of oligoclonal T cells in pan-alphabeta-T cells and clonal evolution during a short clinical course in EBV-HLH with abnormal karyotypes.

Child↗

PubMed2001

The stress-induced MAP kinase p38 regulates endocytic trafficking via the GDI:Rab5 complex.

Early endocytic membrane traffic is regulated by the small GTPase Rab5, which cycles between GTP- and GDP-bound states as well as between membrane and cytosol. The latter cycle depends on GDI, which functions as a Rab vehicle in the aqueous environment of the cytosol. Here, we report that formation of the GDI:Rab5 complex is stimulated by a cytosolic factor that we purified and then identified as p38 MAPK. We find that p38 regulates GDI in the cytosolic cycle of Rab5 and modulates endocytosis in vivo. Our observations reveal the existence of a cross-talk between endocytosis and the p38-dependent stress response, thus providing molecular evidence that endocytosis can be regulated by the environment.

Amino Acid Substitution↗

PubMed2001

Chronic lymphocytic leukemia (CLL) is rare, but the proportion of T-CLL is high in Japan.

Chronic lymphocytic leukemia (CLL) is a rare disease in Japan. Recent advances in molecular biology, diagnostic criteria and classification of CLL have reinforced the concept of each category of CLL as a distinct entity. Since there have been no recent studies on the incidence and prevalence of CLL in Japan, the Kyushu Hematology Organization for Treatment (K-HOT) Study Group conducted two studies of CLL. One study is a prospective registration of newly diagnosed hematological disorders, which gave us some idea of the incidence of CLL in our region (Kyushu island) where adult T-cell leukemia is endemic. A total of 677 patients with hematological disorders were registered over a 6-month period and 11 patients were diagnosed as having CLL among 182 leukemia patients. This amounts to 6% of all leukemias, which is twice as frequent as previously reported in Japan. The other study is a retrospective analysis of CLL. Eleven institutions of the K-HOT Group analysed their diagnostic records of chronic lymphoid leukemia, and 145 patients with CLL were found over a period of 3-12 yr. After the data were reviewed 11 patients were excluded through having a different type of leukemia. The proportion of chronic B-cell lymphoid leukemia was 73% (98/134), while that of T-cell leukemia was 18% (24/134). The proportion of T-cell chronic leukemia was 5-6 times higher than that in Western countries. Two institutions had a complete database on hematological disorders. From this database, the annual incidence of CLL was estimated to be 0.48 per 100 000. Thus, the incidence of CLL in Japan is at least 4-5 times lower than that in Western countries, suggesting that chronic B-cell leukemia is really rare, but chronic leukemia of T-cell lineage develops in Japan as frequently as in Western societies. Further investigation is required to delineate why the incidence of B-CLL is so low in Japan.

Adult↗

PubMed2001

Effects of carbamazepine on the first ovulation in gonadotropin-primed immature female rats.

1. The effects of carbamazepine (CBZ) and its possible mechanisms on the first ovulation were investigated in immature female rats. The first ovulation was induced by administration of equine chorionic gonadotropin (eCG) at 0800 h at 26 days of age. 2. A single s.c. injection of 360 mg x kg(-1) CBZ at 1300 h on the first pro-oestrus (day 28) completely inhibited the first ovulation on the morning of day 29. A marked elevation in 13, 14-dihydro-prostaglandin F2alpha (13, 14H2-PGF2alpha) forming capacity, a sensitive indicator of luteinizing hormone (LH) surge, was not detected in the CBZ-treated group at 0800 h on day 29 (72 h after eCG treatment). The elevation in serum LH levels at 57 h after eCG treatment was not observed in the CBZ-treated group, either. The blocking of the first ovulation and 13, 14H2-PGF2alpha forming capacity were recovered by an i.p. injection of human CG on day 28 in all animals. 3. However, the first ovulation was not blocked by repeated injections of 360 mg x kg(-1) CBZ at 1300 h once daily for 3 days (days 26 - 28). The repeated injections of CBZ caused a great fall (64% decrease) in the serum levels of CBZ at 4 h after the final CBZ injection as compared with the case of a single injection of CBZ and resulted in a delay for 5 h the occurrence of LH surge, which is normally observed around 57 h after eCG injection. 4. A significant increase in the activity of microsomal CBZ catabolism by the repeated injections of CBZ was quantitatively verified by the HPLC analysis. But, the activity of CBZ metabolism in the single injected-animals showed almost similar levels to that in the control. 5. The present results demonstrated that a single injection of CBZ blocks the ovulation by inhibiting LH surge but that the failure of the inhibition of ovulation by repeated injections of CBZ is due to a decrease in serum CBZ levels mediated through CBZ-induced hepatic enzyme induction.

Animals↗

PubMed2001

Intravenous cyclosporine and tacrolimus caused anaphylaxis but oral cyclosporine capsules were tolerated in an allogeneic bone marrow transplant recipient.

A Japanese female patient with angioimmunoblastic T cell lymphoma underwent allogeneic bone marrow transplantation (BMT) from her brother. Cyclosporine at a dose of 3 mg/kg was started by continuous infusion over 24 h on day -1 of BMT. Within a couple of minutes after the infusion was begun, she developed diffuse pruritic erythema on her whole body and tachycardia. The infusion was immediately stopped and corticosteroid was given, resulting in disappearance of the erythema gradually. She was then switched to intravenous tacrolimus. However, she suffered urticalial erythema again. Since polyoxyethylated castor oil, a solubilizer used in the injective formulation of both cyclosporine and tacrolimus, is considered to be responsible for the reaction, she was given oral capsules of cyclosporine (Sandimmun) in which polyoxyethylated castor oil was not contained. No further anaphylactic reaction was observed. The BM cells were successfully engrafted without causing severe GVHD. She was discharged on cyclosporine capsules without any further adverse effects. Anaphylaxis to intravenous cyclosporine and tacrolimus is a very rare but a serious complication. Our present case indicates that oral capsule of Sandimmun is a safe alternative to prevent GVHD in such a case of anaphylactic reaction against intravenous formulation.

Administration, Oral↗

PubMed2001

Eradication of murine brain tumors by direct inoculation of concentrated high titer-recombinant retrovirus harboring the herpes simplex virus thymidine kinase gene.

Implantation of retrovirus-producing cells within a tumor has been demonstrated to eliminate malignant brain tumors effectively in animal models. In our previous study, the implantation of high-titer retrovirus-producing fibroblasts into tumors resulted in highly efficient transduction in vivo. The transduced glioma cells migrated far from the implantation site, potentiating the induction of the remarkable bystander effect. It is also possible, however, that the implantation of murine fibroblast-derived virus-producing cells may induce an immune response in patients. In this study, we prepared retroviruses carrying the herpes simplex virus thymidine kinase (HTK) gene with titers of 1.4--2.5 x 10(11) colony-forming units (c.f.u.)/ml, and stereotactically inoculated only 3 microl of the HTK-bearing retroviruses into the brain tumors of mice. Following repetitive ganciclovir (GCV) intraperitoneal injection, effective killing of glioma cells in the mouse brain was observed. The transduction efficiency was nearly as high as that observed for the implantation of high-titer retrovirus-producing fibroblasts. Eighty percent of brain tumor-bearing mice were completely cured by our treatment protocol using concentrated HTK-harboring retroviruses. Our results suggest that repeated inoculations of high-titer retroviruses carrying the HTK gene followed by GCV treatment may be a promising strategy for the clinical treatment of malignant gliomas.

Animals↗

PubMed2001

Effect of chemotherapy and stem cell transplantation on T lymphocyte clones in familial haemophagocytic lymphohistiocytosis.

Familial haemophagocytic lymphohistiocytosis (FHL) is a rare disorder in infancy, curative only by an allogeneic stem cell transplantation (SCT). We recently confirmed the clonal evidence of T cells in FHL. To confirm the effect of chemotherapy and SCT in FHL, the change of T-cell clones was analysed in two patients using inverse reverse transcription-polymerase chain reaction (RT-PCR) of the T-cell receptor variable region (TCR V) gene, followed by PCR for the junctional region (Jbeta-PCR), a single-strand conformation polymorphism (SSCP) and sequencing analysis at diagnosis, after chemotherapy and after SCT. A high frequency (> 15%) of alphabeta T-cell clones and a predominant bias (Jbeta1:Jbeta2, 85:15) for the Jbeta1 subgroup were observed in the two patients at diagnosis. In one patient, however, an inverted predominant bias (Jbeta1:Jbeta2, 9:91) for the Jbeta2 subgroup and oligoclonal expansion were observed at relapse after chemotherapy. In the other patient, correction of both restricted Jbeta cluster usage and variation of TCR were observed after chemotherapy and SCT. Using sequence analysis, the clonal T cells detected at diagnosis were found to be substituted at low frequency (< 0.75%) by several new clones after chemotherapy and SCT. These results indicate that any genetic defect could influence the regulation of the T-cell network, and normalization of both the variation in each Vbeta repertoire and the Jbeta1/Jbeta2 ratio is needed to achieve remission, and might support the rationale that the only acceptable curative therapy of FHL is allogeneic SCT.

Clone Cells↗

PubMed2001

Novel dinucleotide repeat polymorphism in the first exon of the STAT-6 gene is associated with allergic diseases.

BACKGROUND: T helper-type 2 cytokines, such as interleukin-4 (IL-4) and IL-13, may play a central role in allergic diseases. The protein known as 'signal transducers and activators of transcription 6' (STAT-6) is a key transcription factor involved in both IL-4- and IL-13-mediated biological responses. OBJECTIVE: The objective of this study was to evaluate the possible role of the STAT-6 gene in modulating atopy in the Japanese population. METHODS: We screened all 23 exons of the STAT-6 gene from 10 subjects for mutations by direct polymerase chain reaction (PCR) sequencing. The STAT-6 gene polymorphisms were genotyped by PCR fragment length polymorphism analysis and PCR-SSCP analysis. The IL-4 receptor Q576R polymorphism was also examined by PCR-SSCP analysis. RESULTS: We found a novel dinucleotide repeat polymorphism in the first exon of the STAT-6 gene. The genotypes were classified into four groups according to the number of GT repeats present, from 13 to 16. The frequency of the A1 allele (326 bp, containing 13 repeats of GT) was higher in children with allergic diseases (bronchial asthma, atopic dermatitis and/or food-related anaphylaxis) than controls, although this was not statistically significant (P = 0.0158). In addition, a strong association between the A1 and A3 allele (containing 15 repeats of GT) heterozygote and allergic diseases was identified (P = 0.0002). However, the levels of IgE were not related to the GT repeat polymorphism in the allergic subjects. The GT repeat polymorphism was not associated with the polymorphism in the IL-4 receptor a chain gene (Q576R) and there was no association between the G2964A variant and allergic diseases. CONCLUSION: This suggests that genetic variation in the STAT-6 gene may be associated with predisposition to allergic diseases.

Alleles↗